1. Field of the Invention
The present invention relates to a sensitivity adjustment device, and a radio wave communication device and a watch to each of which the sensitivity adjustment device is applied.
2. Description of the Related Art
In recent years, there have been spread of methods for transmitting and receiving (communicating) various data between electronic devices such as watches each having a wireless communication function, for example, to exchange data between the electronic devices, and to synchronize information therebetween, by a wireless system.
It is possible that data transmitted and received by wireless communications includes many pieces of personal information. Hence, it is necessary to accurately transmit/receive data from a particular electronic device to another particular electronic device in order to protect personal privacy or the like.
However, when there is a plurality of electronic devices around a user, it is possible that an electronic device of the user (main electronic device) cannot have wireless communications with another electronic device with which the main electronic device intends to have the wireless communications (intended electronic device) because the main electronic device causes interference with another electronic device with which the main electronic device does not intend to have the wireless communications (unintended electronic device). In particular, when communications are made in accordance with Bluetooth® which handles radio waves having a long wavelength, the radio waves are not blocked by obstacles, and hence a main electronic device easily causes interference with an unintended electronic device.
Conventionally, as a method for a main electronic device to appropriately establish pairing (namely, an initial recognition operation) with an intended electronic device in a wireless communication system, avoiding interference from an unintended electronic device, for example, U.S. Patent Application Publication No. US 2008/0013601 A1 proposes (i) disposing electronic devices (a main electronic device and an intended electronic device), which are desired to establish pairing with each other, close to each other, (ii) making a query signal, which has an electric power level limited to being smaller than the standard signal output electric power level in a wireless communication system, transmitted from one of the electronic devices, (iii) making an answer signal for the query signal transmitted from the other thereof when the other thereof detects the query signal, and (IV) starting a point-to-point connection between the electronic devices based on a fact that the other thereof answers the query signal first.
When pairing is performed by such a method, a main electronic device can establish pairing only with an intended electronic device, avoiding causing interference with an unintended electronic device.
However, electronic devices transmit and receive data therebetween for various purposes. There are other cases than the case where electronic devices are disposed close to each other to the extent of contacting with each other so as to communicate with each other for pairing or the like. For example, electronic devices having a short distance therebetween transmit/receive various data therebetween, the electronic devices being a portable terminal device and a watch or the like both of which a user wears. Furthermore, electronic devices expected to have some distance therebetween transmit/receive data therebetween, for example, so as to find whereabouts of one of the electronic devices, the one which a user has left somewhere (search function).
Therefore, it is required that sensitivity (reception) of an electronic device to radio waves (radio wave sensitivity) is changed in accordance with its purpose, use, state or the like when the electronic device transmits/receives data to/from another electronic device.
In a mobile phone, a personal computer or the like, the radio wave sensitivity is changed in a communication-related module such as a reception circuit.
In the case where the radio wave sensitivity is changed in a communication-related module, the control mechanism of the module becomes complicated.